To present the defect rate data effectively to the company's board of directors and emphasize the consistency of the number of defects throughout the year, a line graph would be the most suitable choice.
Here is a step-by-step explanation for selecting a line graph:
1. Analyze the Data:
- The given data shows the number of defects per 1,000 units for each month from January (Month 1) to December (Month 12).
- The data points are as follows:
- January: 18 defects
- February: 21 defects
- March: 22 defects
- April: 25 defects
- May: 28 defects
- June: 25 defects
- July: 24 defects
- August: 18 defects
- September: 20 defects
- October: 21 defects
- November: 26 defects
- December: 28 defects
2. Objective:
- The objective is to show that the defect numbers have remained relatively consistent over the 12 months, even though there are some fluctuations.
3. Graph Selection:
- Line Graph: A line graph is ideal for showing trends over a period, such as months. It effectively illustrates how the number of defects fluctuates over time while providing a clear visual representation of the general trend.
- Bar Graph: Though it can show the differences in defect numbers across months, it will not emphasize the trend or consistency as effectively as a line graph.
- Others (Pie Chart or Scatter Plot): These types are less effective in highlighting trends over time.
4. Constructing the Line Graph:
- The x-axis (horizontal) represents the months (1 through 12).
- The y-axis (vertical) represents the number of defects per 1,000 units.
- Plot the defect numbers for each month and connect the data points with a line.
5. Conclusion:
- The line graph will clearly show where the peaks and troughs are and how the defect rates change from month to month.
- It emphasizes the overall consistency in defect rates over the period, despite some variations.
Here is how the line graph would look based on the given data:
```
Month : 1 2 3 4 5 6 7 8 9 10 11 12
Number of Defects: 18 21 22 25 28 25 24 18 20 21 26 28
```
Plotting these points on a line graph would show a clear trend in the defect rates over the year, allowing the production manager to effectively communicate the consistency of the defect rates to the board of directors.
